Dr. 武慧春

洛斯阿拉莫斯国家实验室,美国

Time: 2:00 pm, December 26, 2011

Place: 实验室3楼会议室

Abstract: A double-layer scheme [PRL104, 234801(2010)] is proposed to generate uniform relativistic electron sheets (RES). The generated RES is free of transverse motion, which can dramatically degrade the Doppler shift factor for coherent Thomson scattering (CTS) from 4γ2 to its square root 2γ. The key of the scheme is that the second thicker foil (reflector) completely blocks the laser and the reflected light interacts with RES again to cancel the transverse momentum. Doppler shift factor remains as 4γ2 during CTS. Finally a quasi-monochromatic as XUV/x-ray pulse can be produced. We also develop nonlinear/relativistic CTS theory [PR-STAB14, 070702 (2011)] and find that simply using a circularly polarized light [APL99, 021503 (2011)], our scheme does not need a phase-stabilized laser. Recently, we find that, if laser is obliquely incident onto the double-layer target mentioned above, a giant half-cycle XUV/x-ray (HCX) pulse can be generated [arXiv:1111.2523 (2011)]. For the oblique incidence, the reflected light kicks RES and gives it a transverse momentum, which is simply about tanθ (normalized to mc), θ is the incident angle. The transverse current of RES emits HCX, which co-moves with RES, gets amplified and finally reaches saturation. A Terawatt/24as HCX generation is shown in 2D-PIC simulations. The simple analytical model is also developed and explains the simulation well. HCX will open new era of XUV/x-ray optics and attosecond science, because this is the unique scheme to half-cycle x-ray since the discovery of x-ray more than 100 years ago.